Jool ascent?

[A35K]

Not sure if this is the right place for this, but has anyone tried (and is it at all possible) to get to orbit from "sea level" (or as close as you can get without exploding) on Jool? Searching online I found someone who did it 4 years ago but that was with the old atmospheric models and engines who's thrust wasn't affected by atmosphere. Do any stock engines produce meaningful thrust at 15 atm?

[magnemoe]

23 minutes ago, A35K said:

Not sure if this is the right place for this, but has anyone tried (and is it at all possible) to get to orbit from "sea level" (or as close as you can get without exploding) on Jool? Searching online I found someone who did it 4 years ago but that was with the old atmospheric models and engines who's thrust wasn't affected by atmosphere. Do any stock engines produce meaningful thrust at 15 atm?

back in 0.19 or something Jool had an surface 200 meter below 0 level, you could land there but you would bounce around a lot. I managed to get Jeb down there with an KAS winch from an airship but was unable to plant an flag so I submitted an bug report. 
Next version and the surface was removed you will now explode at -500 meter. This also made Jool transparent so you can see moons on the other side of the planet looking down. 

Back with the old aero model I was able to send an giant ship down to 0 level and out. This is impossible with stock engines today but some has made stock propellers to take them out of the thick atmosphere so they can use rockets to escape. 

[A35K]

Yeah propellers make sense, they would seem to be the only way to do it stock.

[RealKerbal3x]

@EvermoreAlpaca did a Jool ascent a year or so back, using stock props. I don't know if it would be possible using only rocket engines.

 

[Zhetaan]

@A35K:

The only stock engine that has any thrust at all at 15 atm is the Dart.  Nothing else can force out its exhaust against that pressure.  However, (and admittedly, I have not simulated it to check) the Dart's I_sp at that pressure is somewhere around 80.  The only way I can think of doing this--without stock propellers--would be with a multistage spaceplane.  However, I do not know whether that is actually possible; the low thrust of the Dart at that altitude combined with both the thick atmosphere and the high mass of fuel needed to make it up to a 200 km orbit may make it impossible to maintain enough forward speed to lift against the gravity, no matter what wing configuration you use, because unlike Kerbin and all other atmospheric bodies, there's no surface to hold your craft at altitude until you can build up enough speed to take off.

On the other hand, it may be possible to get down to that altitude and make a powered ascent from a forward glide:  call such a craft an atmospheric skimmer rather than a pseudo-lander.  You ought to try it, and if it doesn't work, it's certainly challenge material.

[Snark]

Moving to Gameplay Questions.

[Laie]

According to the Wiki, Jool's atmosphere tops out at 50 (rather than 15) atm. Mammoth/Vector reach zero thrust at 12atm, the Aerospike at 20.

Balloons should be pointless in a hydrogen atmosphere, but I wouldn't be too surprised if they worked (and dirigibles, too). Other than that, propellers -- which also shouldn't get much of a purchase on hydrogen, but the place *feels* as if a paraglider and a pair of flippers would do, so what the hell.

From approx 7-10km upwards, aerospikes will work well enough that a rocket becomes (mathematically) possible. It might be a pancake ten miles wide, though, I didn't bother checking.

 

[bewing]

Laie is right. 1 Kerbin atmosphere is just a little over 100 kPa. Jool's sea level pressure is right about 50 times that. And the Isp of all the engines goes to zero above sea level. Of course, drag is significantly worse than Eve sea level, even at 10km altitude -- so you'll still have all the Eve-style drag problems on the way up.

[A35K]

Thanks for the replies and checking stuff.

Quote

On 1/2/2019 at 3:44 PM, Zhetaan said:

On the other hand, it may be possible to get down to that altitude and make a powered ascent from a forward glide:  call such a craft an atmospheric skimmer rather than a pseudo-lander.  You ought to try it, and if it doesn't work, it's certainly challenge material.

 

 Definitely would be interesting to try, but the anything without a propeller sounds impossible. Using some mod with nuclear jets would make this much more approachable, might give that a try sometime 

[Zhetaan]

2 hours ago, A35K said:

Thanks for the replies and checking stuff.

 Definitely would be interesting to try, but the anything without a propeller sounds impossible. Using some mod with nuclear jets would make this much more approachable, might give that a try sometime 

Then again, you could be surprised.  The first stock Eve SSTO was an entrant into a challenge to see how low in Eve's atmosphere a craft could dip and still return to orbit.  It turned out, with the new aero model, that one could go all the way down.  Obviously, if the pressure is 50 atm, then there's no hope of getting down to datum and living to return even with a forward glide, but that doesn't mean that there isn't something to learn from the attempt.

Edited January 4, 2019 by Zhetaan